Pangolins and Water Bears, Oh My!

“Dad, what’s your favorite animal?”

Unlike most of my posts so far, I don’t have a specific anecdote to go with this one. My son, like most five-year-olds, loves animals. Dinosaurs and cheetahs and sharks in particular, but I don’t think there’s an animal he doesn’t like. He asks me this sort of question quite frequently, and he doesn’t care for answers like “I like them all”. He rightly calls me out on that, with a response that generally boils down to: “No. You have to pick one.”

So, I’m picking one. Two, actually, because one is ridiculously tiny.

First of all, let’s talk about the pangolin. That’s one of these:

Really, do I need to give you any more details? I mean, look at it. It looks like a dinosaur, or something from another planet. What’s not to love?

Depending on the exact species, pangolins can range from one to three feet in length and three to seventy pounds in weight. They’re bipeds, using their tails to balance their heads as they walk on their hind legs. The armored scales are made of keratin (the same stuff as fingernails and rhino horns). They don’t have teeth, so they use their claws and long tongues to dig up ground insects like termites and ants, which are ground up by stones in their gizzard. For defense they roll into armored balls. Sadly, they are also critically endangered.

My *other* current favorite is the tardigrave, also known as the water bear and moss pig, which is a half-millimeter-long… uhm… thing.

It’s an animal, really! As you can see from the picture up there, they look sort of like eight-legged pigs and mostly like something out of a John Carpenter movie. You’ll mostly find them in water drops, but they’ve been seen everywhere. We’ve fired them into space, where they survived dehydration exposure to hard vacuum and to UV radiation doses of “more than 7000 [kiloJoules per centimeter]”. (For the record, that’s 7000 times greater than the recommended safe explsure limit listed by the Canadian Centre for Occupational Health and Safety, the first resource I found on the subject.) Also, it turns out that 17.5% of their DNA derives from other life forms – bacteria, plants, fungi, and Archaea – through horizontal gene transfer. Which is significantly more than most other animals (which average at less than 1%).

I love wierd things. What can I say?

Addendum, 24 December 2015

Just a little more on the Tardigrave.

As scientists are wont to do, another team of researchers tried to sequence the Tardigrave genome.  They were unable to reproduce the results of the other team, finding only about 500 foreign genes – about 1.5% of their DNA.  They estimate that as much as 30% of the DNA sequenced in the original study came from contamination.

So, they aren’t DNA pirates.  But Tardigraves make up for it by secreting glass.  They have genes that code for something called “intrinsically disordered proteins” (IDPs).  These proteins are shapeless and highly flexible under normal conditions, but harden into a solid biological glass when dried out.  The IDP bioglass helps protect essential cell parts until the animal is exposed to water once more.